BERLIN — Germany’s relations with the United States plunged to a low point Thursday, with the government demanding the expulsion of the chief American intelligence official stationed here because, it said, Washington has refused to cooperate with German inquiries into United States intelligence activities. “The representative of the U.S. intelligence services at the United States Embassy has been asked to leave Germany,” a government spokesman, Steffen Seibert, said in a statement. German officials have been frustrated in their efforts to receive clarification from Washington since last summer, when it was reported that the National Security Agency had been monitoring the...